Wire data transmission system
First Claim
1. A wire data collection system having a master station and a plurality of slave stations which are connected in common to said master station by a pair of signal lines, said wire data collection system comprising:
- in said master station,a power source for applying a DC voltage to one of said pair of signal lines via a resistor;
a first data transmission means for short-circuiting said pair of signal lines in accordance with a predetermined period in response to data from said master station to pulse-width encode said data from said master station by said short-circuiting so as to transmit an address signal designating one of said plurality of slave stations, and for subsequently transmitting a response clock pulse having said predetermined period to each of said plurality of slave stations; and
a first data reception means for detecting the change of a pulse width of a DC voltage on said one signal line when said response clock pulse is transmitted to receive data from the slave station designated by said address signal; and
in each of said plurality of slave stations,means for detecting a change of a pulse width of a DC voltage across said pair of signal lines to identify said address signal;
a second data transmission means for short-circuiting said pair of signal lines in synchronism with said response clock pulse when the slave station is designated by said address signal to encode said data from said slave station as a change of the pulse width of said response clock pulse so that said data from the designated slave station is transmitted to said master station.
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Accused Products
Abstract
In a wire data transmission system which transmits data from a master station to a number of slave stations or vice versa through a pair of signal wires connected in parallel with each other, only the master station need be provided with a data transmission power source. Signal lines receiving DC voltage from the power source through a resistor are periodically short-circuited within the master station, thereby to transmit "1" or "0" encoded data according to the duration of the short-circuiting time of the signal lines, along with an identification code which designates a slave station. In the slave station, a variation of a voltage between the signal lines is detected, so that the slave station receives the identification code and encoded data from the master station, and a state of short circuit between lines corresponding to encoded data or a clock pulse from the master station is changed by short-circuiting the signal lines, so that the slave station transmits the encoded data to the master station. The master station detects the change of the code transmitted therefrom to receive the encoded data from the slave station. When a short circuit fault occurs between the lines in the number of slave station equipments connected in parallel to the pair of signal lines, the slave station in which the short circuit fault has occurred is automatically isolated from the pair of signal lines.
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Citations
11 Claims
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1. A wire data collection system having a master station and a plurality of slave stations which are connected in common to said master station by a pair of signal lines, said wire data collection system comprising:
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in said master station, a power source for applying a DC voltage to one of said pair of signal lines via a resistor; a first data transmission means for short-circuiting said pair of signal lines in accordance with a predetermined period in response to data from said master station to pulse-width encode said data from said master station by said short-circuiting so as to transmit an address signal designating one of said plurality of slave stations, and for subsequently transmitting a response clock pulse having said predetermined period to each of said plurality of slave stations; and a first data reception means for detecting the change of a pulse width of a DC voltage on said one signal line when said response clock pulse is transmitted to receive data from the slave station designated by said address signal; and in each of said plurality of slave stations, means for detecting a change of a pulse width of a DC voltage across said pair of signal lines to identify said address signal; a second data transmission means for short-circuiting said pair of signal lines in synchronism with said response clock pulse when the slave station is designated by said address signal to encode said data from said slave station as a change of the pulse width of said response clock pulse so that said data from the designated slave station is transmitted to said master station. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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Specification